(a) Field of the Invention
The present invention relates to a differential for a part-time 4-wheel drive vehicle, and more particularly, to a differential for a part-time 4-wheel drive vehicle that is equipped with a power cut-off device for preventing power from reversibly transmitting from the front wheels through a front propeller shaft to a power transfer case.
(b) Description of the Related Art
Generally, a part-time 4-wheel drive vehicle can be changed by the operator from a 4-wheel drive mode to a 2-wheel drive mode and vice versa. FIG. 1 shows a drive train of a conventional part-time 4-wheel drive vehicle. The terms "front" and "rear" as used herein shall mean and refer to the respective forward and rearward directions of the vehicle body. Mounted on an output side of a transmission 52 is a power transfer case 53 that is used for selectively transmitting power to either both or one of the front and rear wheel sets 60 and 57, according to a drive mode of the vehicle.
That is, the power transfer case 53 is connected to a rear differential 55 via a rear propeller shaft 54 to transmit power to a rear axle shaft 56 supporting the rear wheels 57. The power transfer case 53 is further connected to a front differential 70 via a front propeller shaft 58 to selectively transmit power to a front axle shaft 59 supporting the front wheels 60.
Accordingly, in 4-wheel drive mode, the power transfer case 52 transmits power to both front and rear wheel sets 60 and 57, and in 2-wheel drive mode, to only the rear wheel set 57.
However, in 2-wheel drive mode, power generated by the rotation of the front wheels is reversibly transmitted to the front propeller shaft 58 through the front axle shaft 59, resulting in power loss and generation of noise.
To solve the above problems, a power cut-off apparatus such as a free wheel hub system or a center axle disconnecting system have been provided between the front axle shaft and the front wheels to cut-off the power transmitted from the front wheels to the front propeller shaft.
However, the above well-known prior power cut-off apparatuses have large, complicated structures, which increases manufacturing costs.